To continue on the topic of my previous post, I introduce you some tips under Linux (Ubuntu & Debian distributions) and general tips to increase your laptop’s battery life.

Turn off the screen

You have to make a phone call, go through a document or… a body need. During this time, you often leave your computer on. Rather than keeping your monitor on or suspending the system (note that when the system wakes up, it consumes a great amount of energy), why not turn the screen off temporary with a single click?

For this, you just have to create a launcher (shortcut) and configure it to execute this command:

xset dpms force off

Then, it can be added to your taskbar or desktop. For daily use, you can also assign it to your own keyboard shortcut.

The acronym DPMS stands for Display Power Management Signaling. It is a command line program that allows power saving behaviour of monitors when the computer is not in use. Other options are available. You can read this post for more information.

CPU Scaling

CPU Scaling is a feature built into most modern mobile CPUs that allows them to scale up or down in how fast they run (the frequency). If you have a fairly modern mobile computer there is a very good chance that your CPU can handle frequency scaling. For example, my five-year-old computer is based on an Intel Centrino CPU which supports it !

It is a pity that your processor runs at full speed if you are using a word processing or surfing the internet. Unless you are editing a movie or playing video games, this enables you to extend the use time of your laptop.

The idea is to “underclock” the processor when it is not fully stressed by your applications. A processor can save energy by running slower. Unfortunately, this will result in a slight performance degradation. So you have to find the good compromise.

Processors handle scaling differently. Various frequencies and modes are available depending on your model. To know yours, you need to install and activate the “CPU Frequency Scaling Monitor” applet.

Here is a short explanation for each mode:

“Powersave” will keep the CPU constantly at the lowest frequency. This mode is very useful to preserve the battery;

“Ondemand” will set the CPU at the lowest frequency until use of the CPU increases, then it will automatically set it up to the highest frequency. This is generally the default mode;

“Performance” simply sets the CPU at the highest available frequency. It is better to have your laptop plugged-in while using this mode;

“Conservative” is quite similar to the « Ondemand » mode. Your CPU will go up as needed, starting at the lowest frequency, and then setting up to the next available frequency (not the highest). It is the best compromise when you do not pay too much attention to your battery;

Finally, you also have the possibility of setting manually the frequency. In my case, I have four choices (0.798 GHz, 1.06 GHz, 1.33 GHz and 1.73 GHz).

GPU Scaling

The graphics card is also very energy-consuming. Following the example of the CPU, it is possible to put its chip into a low voltage mode. In my example, I use an ATI graphics card. It does seem that Nvidia provides a similar software.

We will use the command line tool “ATI Powerstate” available when you install the official driver. In the same time, we will make it more user-friendly for daily usage by adding a GUI.

In my case, I have two power states available. You can have more choices depending on the model of your graphic chip. Thus, it can be necessary to modify the script. By default (whether the laptop is plugged-in or not), the graphic card will run at full speed.

After selection, a tooltip shows up to confirm you about the running mode.

Once again, you will be in a dilemma, choosing between energy saving and a decrease in performance. For example, the greatest 3D effects are a little bit jerky when I activate the idle mode.

Still and always the good practices…

Except these few tips which have required the installation and/or the use of specific software, there are no secrets to preserve the energy of your battery ! There are still the good practices, the ones that have always been known to work on any computer and under any operating system. Here is a non-exhaustive list:

Disconnect your external devices when you do not use them: hard drive, USB stick, mouse, webcam or any USB powered device;

Deactivate wireless technologies (WI-FI and Bluetooth) when you do not use it;

Close the applications you do not use. Multitasking stresses the CPU and storing lot of information in memory consumes energy;